WASHINGTON — Some of President Obama’s email correspondence was swept up by Russian hackers last year in a breach of the White House’s unclassified computer system that was far more intrusive and worrisome than has been publicly acknowledged, according to senior American officials briefed on the investigation.
The hackers, who also got deeply into the State Department’s unclassified system, do not appear to have penetrated closely guarded servers that control the message traffic from Mr. Obama’s BlackBerry, which he or an aide carries constantly.
But they obtained access to the email archives of people inside the White House, and perhaps some outside, with whom Mr. Obama regularly communicated. From those accounts, they reached emails that the president had sent and received, according to officials briefed on the investigation.
White House officials said that no classified networks had been compromised, and that the hackers had collected no classified information. Many senior officials have two computers in their offices, one operating on a highly secure classified network and another connected to the outside world for unclassified communications.
But officials have conceded that the unclassified system routinely contains much information that is considered highly sensitive: schedules, email exchanges with ambassadors and diplomats, discussions of pending personnel moves and legislation, and, inevitably, some debate about policy.
Officials did not disclose the number of Mr. Obama’s emails that were harvested by hackers, nor the sensitivity of their content. The president’s email account itself does not appear to have been hacked. Aides say that most of Mr. Obama’s classified briefings — such as the morning Presidential Daily Brief — are delivered orally or on paper (sometimes supplemented by an iPad system connected to classified networks) and that they are usually confined to the Oval Office or the Situation Room.
Still, the fact that Mr. Obama’s communications were among those hit by the hackers — who are presumed to be linked to the Russian government, if not working for it — has been one of the most closely held findings of the inquiry. Senior White House officials have known for months about the depth of the intrusion.
“This has been one of the most sophisticated actors we’ve seen,” said one senior American official briefed on the investigation.
Others confirmed that the White House intrusion was viewed as so serious that officials met on a nearly daily basis for several weeks after it was discovered. “It’s the Russian angle to this that’s particularly worrisome,” another senior official said.